This invention relates generally to laser scanning apparatus and more particularly to compact, self-contained laser scanning modules for use in various type of laser scanning systems.
Various laser-based scanning systems have been disclosed in the patent literature and many are commercially available to read bar codes, e.g., the uniform product code, which is imprinted on packaging for product, or on the product itself, or on some other item.
One type of scanning system is referred to as a counter or "slot scanner". Such devices are generally mounted within a housing in a checkout counter of a supermarket or other retail establishment, and include a window at the top thereof through which a scanning pattern is projected. The scanning pattern is created by a laser and associated optical components, e.g., mirrors, etc. which typically produce plural scan lines which are either parallel to one another and/or intersect one another. When an item bearing a bar code is brought into the field of the scan pattern so that the pattern traverses the bar code light is reflected off of the bar code and is received back through the window of the slot scanner, whereupon decoding means converts the received light into an electrical signal indicative of the bar code. These signals can then be utilized to identify the article bearing the code and provide pricing information.
In order to ensure that a bar code is traversed sufficiently so that it can be read accurately irrespective of its orientation within the scan pattern, prior art counter scanners have utilized various optical configurations including mirrors, prisms, and the like to fold the laser beam and create complex patterns. Examples of such patterns are comb patterns, orthogonal patterns, interlaced patterns, star-like patterns, etc. While such patterns may be suitable for their purposes, the means for creating them has resulted in housings which were quite large in size.
In my U.S. Pat. No. 4,713,532 there is disclosed a counter scanner producing a pattern having at least three intersecting scan lines forming a large "sweet spot" to enable the bar code to be read irrespective of its orientation with respect to the scanner. That scanner is housed within a very compact, small footprint housing, e.g., a housing taking up an area no greater than approximately one hundred and fifty square inches of counter space and having a height of less than six inches. Notwithstanding the compact features of that scanner, it is obviously still too large and heavy to be utilized in a hand-held scanning system.
Hand-held scanning devices commonly make use of a lightweight and compact scanning head which is arranged to be held within the user's hand. The head, when actuated by the user projects a laser beam pattern out of a window in the head onto a bar code located opposite the window. In U.S. Pat. No. 4,575,625, of which I am the inventor, and which is assigned to the same assignee as this invention, there is disclosed one such a self-contained hand-held laser scanner. That scanner's head includes the bar code scanning means, power supplies, a decoding computer and communication capabilities to enable the uploading/downloading of data to and from the scanner, all located within a molded plastic body or housing. In particular the housing includes a laser tube which produces a laser beam and directs it to a rotating reflective polygon. The polygon is rotated by an associated motor assembly. The laser beam is swept by the rotating polygon through a predetermined arc and is directed out through a window in the housing to sweep across a bar code located opposite the window. A photo detector located within the housing receives the light reflected off of the bar code and converts that light into an electrical signal which is amplified and processed by an associated amplifier and signal processing circuitry, also located within the housing. A low voltage power supply, a microprocessor and associated circuitry, a high voltage power supply, a releasable input/output cable connector or plug, an associated input/output cable, and an on/off trigger assembly complete the scanner and are also located within the housing. The shape of the housing is shown in U.S. Des. Pat. No. D281,977, also assigned to the same assignee as this invention.
In my co-pending U.S. patent application Ser. No. 07/128,299, filed on Dec. 3, 1987, now U.S. Pat. No. 4,805,175, entitled Ultra Compact, Hand-Held Laser Scanner, which is assigned to the same assignee as this invention, there is disclosed an even more compact hand-held scanner. That scanner basically comprises a laser tube and associated high voltage power assembly, beam folding and sweeping optics and a motor sub-assembly, a photo detector and associated amplification and signal processing circuit sub-assembly, a releasable input/output cable connector or plug, an associated input/output cable, and on/off trigger assembly, all housed within an extremely compact and ergonomically designed housing. The housing includes a short snout or body portion in which a window, through which the laser beam and the reflected light passes, and a supporting, hand-grip portion arranged to be held within the user's hand. The housing's construction enhances the balance point of the scanner by putting its center of gravity in the operator's hands so that it can be held comfortably for long periods of time, without operator fatigue.
In the interest of compactness the device of my co-pending application makes use of an oscillating mirror to effect the scanning or sweeping action of the beam. Thus, in that scanner the laser beam is directed to an oscillating mirror to sweep the beam through a predetermined arc, with the swept beam being directed straight from the mirror through the short snout body portion of the housing and out through the window to impinge on a bar code disposed opposite the window.
Examples of other hand-held laser scanners have been disclosed in the following patent literature: U.S. Pat. Nos. 4,387,297 (Swartz et al.), 4,409,470 (Shepard et al.), 4,460,120 (Shepard et al. ), 4,607,156 (Koppenall et al.) and 4,760,248 (Swartz et al).
While the devices disclosed in the aforementioned prior art all exhibit the characteristic of being compact to some degree in the interest of operator ease of use, nevertheless all still leave something to be desired from the standpoint of size.
As will be appreciated by those skilled in the art, if the angle through which the beam is swept is small, the linear velocity of the beam when traversing a symbol located close, e.g., 1 inch, to the beam sweeping mechanism (e.g., mirror) will not vary so greatly from the linear velocity of the beam when traversing a symbol located far, e.g., 10 inches, therefrom that the signal processing and decoding components can readily compensate for such speed differences. Where, however, a large beam sweep angle is utilized (such that the scanning of large, close-in, symbols can be readily effected) there will be a great difference in the linear beam speed when scanning up close and far out symbols. Thus, the task of signal processing and decoding the light reflected off of small (narrow) symbols located far from the scanner becomes considerably more difficult.
Placing the outgoing beam window closely confronting the beam sweeping mirror, like that done in U.S. Pat. No. 4,409,470 (Swartz, et al.) so that the beam passes over the barrel portion of the housing and is not constrained thereby, results in a large scanner housing (i.e., its barrel portion is of substantial length). Placing the outgoing mirror closely confronting the beam sweeping mirror, like that done in the U.S. Pat. No. 4,760,248 (Swartz, et al.), enables the use of a compact scanner housing. However, that construction is inconsistent with the production of a wide-beam length scan pattern closely adjacent the window using a small beam sweep angle, such as would be necessary to obviate the scan velocity problems inherent in scanning small symbols at great distances, as described above.
Accordingly, the need presently exists for a scanner which can produce a narrow beam sweep angle consistent with the scanning of small symbols at large distances, while enabling the beam to be of sufficient width up close to the window consistent with the decoding of large symbols located thereat, yet all located within a very compact housing.
Moreover, a need presently exists for providing a self-contained scanning device which is very compact in size and light in weight and which can serve as a module or basic building block (an "engine") for incorporation into either a hand-held laser scanning system or other types of laser scanning systems.